Exam MCIA - Level 1 topic 1 question 15 discussion

An integration Mule application is being designed to process orders by submitting them to a backend system for offline processing. Each order will be received by the Mule application through an HTTPS POST and must be acknowledged immediately. Once acknowledged, the order will be submitted to a backend system.
Orders that cannot be successfully submitted due to rejections from the backend system will need to be processed manually (outside the backend system).
The Mule application will be deployed to a customer-hosted runtime and is able to use an existing ActiveMQ broker if needed.
The backend system has a track record of unreliability both due to minor network connectivity issues and longer outages.
What idiomatic (used for their intended purposes) combination of Mule application components and ActiveMQ queues are required to ensure automatic submission of orders to the backend system, while minimizing manual order processing?